Patient positioning during medical tests such as X-ray imaging, computer tomography (CT), and positron emission tomography (PET) impacts not only the appearance of the resultant images, but, more importantly, the interpretation of those images. Similarly, with respect to patient treatment, such as radiation therapy, proper patient positioning can aid in targeting cancerous tissue and reducing radiation reaching healthy tissue. Especially useful would be an ability to match patient positioning when conducting subsequent procedures or tests for the same medical condition.
Patient positioning for medical images, such as portable X-rays, can be critically important to a radiologist's ability to accurately interpret a resulting image. This is true whether the images are taken at bedside on the floor, in an Intensive Care Unit (ICU), or other venue. The quality of a radiologist's interpretation can be affected by the position of the patient in several different ways. For example, it is very useful for a radiologist to know the position of the patient overall during the X-ray procedure relative to being upright or supine in order to more effectively interpret an image. Such position information can be used to account for fluid in the pleural space that can shift depending on position. Since the appearance of blood vessels also changes based on position, a radiologist can also use position information obtained during imaging to interpret the appearance of blood vessels in the lung.
Another aspect where positioning is important concerns comparisons between studies. It is quite useful to have patients positioned in the same way for a series of studies, thus allowing a subsequent image to be acquired with substantially the same parameters. As a result, when images acquired at different times are compared it is easier to detect actual changes in the patient's body because comparative changes in the image due to technical parameters will have been mitigated. Unfortunately, a reliable system for such position matching is not readily available.
With respect to radiation treatments, for example, medical technicians employ relatively rudimentary position marking methods such as applying dots to the patient's skin with a felt tip marker. The technician then attempts to locate the markings by eye. When repeated tests are needed over a period of time, variables such as changing personnel may adversely impact proper patient positioning.
As a further example, following a CT and/or PET scan, a technician may draw special colored lines on a patient's skin with ink. Semi-permanent lines drawn on the skin are used to outline treatment fields in an attempt to assure that the patient will be correctly positioned each time the patient receives a treatment. The lines are intended to remain until the course of therapy is completed.
Further, with respect to patient treatment, targeting of the lungs during radiation treatment presents a challenge to radiation oncologists. A target tumor or lesion in a lung, like the lung itself, is constantly, moving during treatment. One method used to account for respiration movement is called “respiration gating.” For treatment to be effective without the benefit of respiration gating, a larger area of the lung, usually including more healthy tissue, is irradiated to ensure that the target tumor is kept within the radiation beam. With respiration-gated radiation therapy, the radiation beam is targeted in real time with the breath to a specific point in the cycle of respiration as measured by a respiration belt around the patient. Radiation gating reduces the amount of healthy lung receiving radiation, so a higher dose of radiation can be used. Gating can also reduce the time of treatment. As currently practiced, respiration gating is tied to the respiration cycle and not to real time patient positioning data as may be provided by the systems described herein.
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